ldentle

A/C Pressure Sensor on PCM 411 2002 express van tune



Has anyone ever ran across this situation. I have a 411 PCM with a tune from a 2002 Chevy Express Van . Also I have a Vintage Air A/C system installed in which I wired to use an A/C pressure sensor (22664328) in order for the PCM to control the A/C unit . I changed my AC Type in the tune to analog , The fans and A/C clutch relay comes on when the engine is running, everything appears to work OK except for the A/C pressure Sensor. The fan and A/C clutch relay works whether or not the A/C pressure sensor is installed . Can't figure out why the PCM is not looking for the output from the A/C pressure sensor. The A/C pressure sensor is wired C2-14 red , C2-57 violet , C1-45 gray , A/C clutch relay coil C2-43 and relay contact to C2-18 just like the 2002 Camaro. MY understanding is the PCM should not turn on the fan and A/C clutch relay unless it see the output from the A/C pressure sensor and the engine is running at 550 rpm.

Any help is appreciated

G-Body

iTrader: (4)

You probably won`t be able to get it to recognize the pressure sensor. I have never tried to change the pressure sensor/switch style on a 411 PCM, but I have tried on the newer green/blue PCM`s and it is not possible on them, at least not if the OS does not allow it from GM.

The 411 vans that I have seen schematics for all used a high and low pressure switch setup instead of the truck/f-body style pressure sensor. What OS # are you using?

ls1nova71

iTrader: (4)

Yep, 2002 express vans don't use the three wire pressure sensor. Why aren't you running an F body tune? Seems like that would be your easiest fix.

garys 68

iTrader: (1)

I think you're being given the right direction here.
The 411 ecu was being used with trucks/vans with 2 wire pressure sensors and the 3 wire in fbody/vette with variable displacement compressors.
There's also the issue with DBW (used in trucks and vettes) and cable TB (used in trucks anf F bodies).
If you're looking for a stock tune, you might want to keep these consistent.

RicOtt

You have wired the pressure sensor up like a Camaro - Just verified the pinouts you gave as the camaro setup. A truck/van tune will not run this setup. The truck setup has two "pressure" switches - it is a totally different wiring setup. You did not mention wire C2-17. On a camaro tune this wire is the "AC Request" (the AC on switch from VA). Is it wired up? Where do you have the AC request wired?

Good luck, when you get it working it is great (just like the factory!!!)
Ricky

ldentle

I think you guys are right the 2002 Van tune uses two pressure switches and the OS will not recognize pressure sensors . But that's fine , because I'm using the 2002 van tune to run a TPI setup. As long as the PCM is controlling the A/C then that's OK. Wired as I have it and using the van tune the A/C clutch and fan will not engage unless the engine is running above 500 rpm. I think the key to this setup is having C2-18 wired to the relay contact which tell the PCM the A/C clutch is engaged. Without C2-18 neither clutch or fan will engage . My A/C system is a Vintage Air unit which I wanted to signal the PCM 's "AC request " to control the A/C clutch and fan. I just found out it's all in the OS that you use.

garys 68

iTrader: (1)

Just an FYI, I'm running both Vintage and Classic auto air on LS motors. Neither uses any ecu signal or control. No issues ever.
I run 1 fan of the ecu temp, the other off a trinary switch and/or ecu engine temp control.

ldentle

Yes ,I understand you can run the fans from ecu temp and trinary switch , but the fan needs to be running as soon as the A/C compressor is started in order to cool the condenser . Your way the condenser is not cooled until the engine reach operating temp or the hi side pressure is high enough to trigger the trinary switch to turn the fans on . Your way may work but I think letting the PCM control it is better. This way the condenser is being cooled soon as the A/C compressor starts.

Thanks for the info.

69 Ghost

You need to do your homework on this. The issue comes up all the time. The pressure sensor is used with a variable compressor because it runs constantly and does not turn on and off like a normal fixed compressor does. Variable=pressure sensor, Fixed=pressure switch. The fan setup is another portion of the OS where you need to tell it how many fans it has. The wiring and programming are based on the compressor type. The fan setup is wired and programmed based on the fan setup. They are mutually exclusive. I have heard that HP tuners does not work properly when trying to change the compressor type. I cannot verify that but Tunercat works. I have tested and run both on my car with a 411 and a 243 PCM. I just recently ditched my Vintage Air for a factory box setup using a variable with orifice tube and 2 fans on a 04 GTO OS turning it on with a 12 volt A/C request all the wiring is based on a 02 Camaro. The 411 was used on a number of vehicles both DBW and DBC along with single and dual fans, and fixed and variable compressors. First you should test for the fans if you have dual fans, then get the compressor to turn on/off according to how you want it to work. The fans should follow once you get everything in place.